Rotary percussion drill assembly



Ffib. 10, 1953 J BAKER ROTARY PERCUSSION DRILL ASSEMBLY 3 Sheets-Sheet 1Filed July 12, 1947 INVENTOR: 014M HIS ATTORNEYS Feb. 10, 1953 J. B.BAKER ROTARY PERCUSSION DRILL ASSEMBLY ,3 Sheets-Sheet 2 Filed July 12,1947 INVENTOR:

WWW/WM HIS ATTORNEYS Feb. 10, 1953 J. B. BAKER 2,628,115

ROTARY PERCUSSION DRILL ASSEMBLY Filed July 12, 1947 3 Sheets-Sheet 3INVENTOR: M 13 Ran (m, BY am/6 H IS ATTORNEYS Patented Feb. 10, 1953UNHED STAT 5 I v in;

TENT OFFICE ROTARY PERCUSSION DRILL ASSEMBLY Application July '12,1947,]Serial N 760,643

7 Claims. 1

This invention relates to rotary precussion drills of the kindcomprising a drill rod and a separate drill bit having an axial socketat the end remote from the cutting end adapted to receive one end of thedrill rod. Drill rods and bits of this general type are usually providedwith interengaging threads, clamps, keys or other special securingdevices, which are expensive and difficult to produce and involve dangerof slippage or separation of the parts.

The present invention is concerned with overcoming disadvantages, suchas those above mentioned. Its principal object is to provide a strongand durable connection between the 'bit and drill rod which will preventrelative rotary movement and accidental disengagement thereof and whichis simple to produce and which will eliminate separate fasteningdevices.

The invention consists principally in providing the circumferential wallof the drill rod receiving socket of the bit with one or morelongitudinal slits having one side edge offset inwardly relative to theother side edge so as to provide a shearing edge adapted to bite intothe peripheral surface of the portion of the drill rod in said socketand thus prevent relative rotary and endwise movement of said drill rodand bit. The invention also consists in the drill bit and in the methodemployed in producing the inwardly oliset edge of the slit.

In the accompanying drawings, which form part of this specification andwherein like symbols refer to like parts wherever they occur,

Fig. l is a side elevational view of a rotary percussion drill embodyingmy invention,

Fig. '2 is a cross-sectional View on the line 2"2 in Fig. 1,

Fig. 3 is a central longitudinal sectional'view on theline 3-3 in Fig.2,

Fig. 4 is an end elevational view of the drill rod receiving end of thebit before the attachment thereof to the drill rod,

Fig. 5 is a central longitudinal sectional view of said bit on the line55 in Fig. 4,

Figs. 6, '7, 8, 9 and 10 are views similar to Fi s. 1, '2, 3, 4 and 5,respectively, showing a modified form of drill, I

Figs. l1, l2, l3 and 14 are views similar to Figs. 4 and 9 illustratingfour further modifications of the invention; and

Fig. 15 is a view similar to Fig. 5, showing another drill of slightlymodified form.

In Figs. 1 to 5, my invention is-shown-embodied in a rotary percussiondrill bit comprising a cylindrical drill rod A and a separate drill bit13.

2 The drill rod A has an axial passageway ltherethrough for thecleansing fluid or liquid used during the drilling operation.

The separate drill bit B comprises asubstantially cylindrical bodyhaving a cylindrical axial socket 2 in one end adapted to snugly receiveone end of the drill rod A and an axial passageway 3 leading from thebottom of said socket to the other or cutting end of said bit forconveying thereto cleansing fluid receivedirom the axial passageway 'iin the drill red A. The drill bit 3 is shown provided with aconventional cruciform cutting end comprising cutting teeth '4 that aredisposed radially of the axial passageway'3 of said bit and extendoutwardly of the cylindrical body thereof where they are supported bythe usual ribs or buttresses '5 that are spaced apart circumferentiallyof said body exteriorly thereof and taper toward and merge into saidbody near the socket end thereof.

According to the present invention, the circumferential wall of thedrill rod receiving socket 2 of the bit B is provided with a series ofciroumferentially spaced radial slits 6 which extend downwardly parallelto the longitudinal axis of said bit between the exterior buttresses 5from the mouth or open end-of said socket and terminate short of thebottom thereof in wide circular lower end portions 1. Each slit 6 ispreferably arranged with one edge at or closely adjacent to one of thetwo buttresses 5 between which said slit is located; and said ed e ofsaid slit is offset inwardly to form in the socket 2 a shearing edge 8ada ted to' grip or bite into the eripheral surface of the socketengaging portion of the drill rod A and thereby prevent relativerotary'movement' of said drill bit androd. The shearing ed e 8 of eachslit 6 sinks into the drill rod 'A above the lower end thereof and thusalso servesto prevent the :bit B from coming off said drill rod.

While mechanical pressure may be employed to forceone edge of the slits6 inwardly to form the shearing edges 8 and to press them into the periheral surface of the socket engaging portion of the drill rod A, I havediscovered that the .inwardly offsetting of said edge of said slit maybe brou ht about by heating the annular side wall of the socket Z to atemperature approaching snring temper and corresponding "hardnessandthen "quenching the heat treated wall. This method of offsetting one'edge of the 'slit i's based upon the well known principle thata'hea'vy'ring section contracts "more than a light ring section afterheat treating and -'quenching. "Ihus, during the quenching operation,the heavy section provided by the exterior buttress along one edge ofsaid slit 6 in the circumferential wall of the socket 2 of the bit Bcauses the thick buttressed section of said wall to shrink a greateramount than the thin section thereof along the other edge of said slitand move inwardly relative to said other edge to form the inwardlyoffset biting edge 8 which sinks into the socket engaging end of thedrill rod A.

The modified drill construction shown in Figs. 6 to 10, inclusive, issimilar to that shown in Figs. 1 to 5, inclusive, except that the socket2 of the bit B and the socket engaging end of the drill rod A arecorrespondingly tapered, as at 9, and the slits 5* pass through thecircumferential wall socket at oblique angles to the center of the saidsocket. That is, either side of the slits, since both sides of the slitare parallel, is contained in a plane which is directed at an obliqueangle to a radially directed plane containing an edge of the slit. Theresulting chordwise arrangement of the slits 6 provides sharp acuteangled cutting edges 8 along the inwardly offset edges thereof, theoblique angle of said cutting edges serves to resist endwise separationof the drill rod and bit and the correspondingly tapered portions of thesocket and the rod end therein compensate for the greater contraction ofthe circumferential wall of the socket at the bottom thereof where thewall is of thicker section due to the tapered buttresses of the bit.

The modified bit B shown in Fig. 11 is similar to that shown in Figs. 1to 5, inclusive, except that the slits 6 of the modified bit are locatedmidway between the buttresses. In this construction, mechanical pressureis employed to force one edge of each slit inwardly to form the shearing edge.

In the modified construction shown in Fig. 12, i

the drill rod receiving socket 2 of the bit B is of hexagonal shape. Theslits 6 pass through the circumferential wall of the fiat-sided socket 2at an oblique angle to the center thereof and are disposed parallel tothe longitudinal axis thereof. The slits 6 open into the socket 2through two diametrically flat side faces thereof midway of the width ofsaid faces.

The modified construction shown in Fig. 13 is also provided with ahexagonal drill rod receiving socket 2 and two diametrically opposedslits 6 which extend through the wall at oblique angles. In thisconstruction, however, the slits 8 open into the fiat-sided socket attwo diametrically opposed corners thereof.

The modified bit shown in Fig. 14 has a four sided socket 2 with roundedcorners and the slits 6 open into said socket at the rounded cornersthereof.

' The drill bit shown in Fig. 15 is similar to that shown in Fig. 5,except that the slits 6 are of uniform width from top to bottom, insteadof having enlarged lower end portions. With this arrangement, theinwardly offset edge of the slit will draw in more at the bottom than atthe top under heat treatment.

In each of the hereinbefore described drill constructions, the inwardlyoffset cutting or shearing edges of the longitudinal slits in thecircumferential wall of the drill rod socket of the drill bit bite intoand interlock with the peripheral surface of the portion of the drillrod in said socket and thus prevent relative rotary movement and endwiseseparation of said drill 4 rod and bit. In the construction shown inFig. 11, one side of the slits is forced inwardly by mechanical pressureto form the shearing edges of the slits. In the other constructions, theinwardly offset cutting edge may be produced by mechanical pressure orby heating and quenching the circumferential wall of the socket so thatthe thick buttressed portion of the wall contracts to a greater extentthan the thinner portion of said wall without the buttress. The circularlower end portions of the slits provide terminals for the slitting tooland facilitate heat treating, but these enlarged lower end portions maybe omitted, as shown in Fig. 15. In heat treating the bit, the cuttingedges of the slits are given a spring temper and are hard enough to biteinto the softer metal of the drill rod. The oblique angle at which theslits extend through the circumferential wall of the socket providessharp acute angled cutting edges along the inwardly displaced edges ofthe slits; and the oblique angle of said cutting edges relative to thelongitudinal axis of the bit serves to prevent endwise separation of thebit and drill rod. The drill rod and socket may be of any desired shape;and one or more slits may be employed. The circumferential spacing,angle and number of the slits may also be varied as well as the numberand arrangement of the cutting edges of the bit. While it is preferableto first offset the edges of the slits and then force the drill steelinto the socket of the bit, the edges of the slits may be offset intogripping engagement with the drill rod after the latter is inserted inthe socket of the bit.

What I claim is:

-1. In a rotary percussion drill comprising a drill bit provided with anaxial socket having a circumferential side wall with circumferentiallyspaced buttresses on the outer periphery thereof and a drill rod havinga portion disposed in said socket, the improvement which consists inproviding said wall between buttresses with longitudinal slits, onemargin of each of which is offset inwardly into permanent interlockingengagement with the peripheral surface of the socket engaging portion ofsaid rod.

2. The combination set forth in claim 1 wherein the inwardly offsetmargin of at least one of said slits terminates short of the bottom ofsaid socket and the corresponding end of the rod therein.

3. The combination set forth in claim 1 wherein the inwardly offsetmargins of said slits have acute angled inner longitudinal cutting edgesadapted to bite into the peripheral surface of said rod.

4. The combination set forth in claim 1 wherein said slits are eachcontained in a plane directed chordwise of said socket at an obliqueangle to a radially directed plane containing an edge of the slits.

5. The combination set forth in claim 1 wherein said socket and theportion of the rod disposed therein have flat sides and the slits openinto said socket substantially midway of the width of said sides.

6. The combination set forth in claim 1 wherein said socket and theportion of the rod disposed therein have fiat sides and the slits openinto said socket at the corners formed by the flat sides thereof.

7. The combination set forth in claim 1 wherein said slits are locatedcloser to one than the other of the buttresses between which they areNumber located. 2,322,420 JOHN B. BAKER. 2,370,603 2,375,741 REFERENCESCITED 5 2 421 32 The following references are of record in the file ofthis patent:

Number UNITED STATES PATENTS 405,782 Number Name Date 10 423,343

547,400 Palmiter Oct. 1, 1895 Name Date Craig June 22, 1943 ZimmermanFeb. 2'2, 1945 Dibner May 8, 1945 Baker June 10, 1947 FOREIGN PATENTSCountry Date Great Britain of 1934 Germany of 1926

